Automatic multiple-sample multiple-reagent chemical analyzer

ABSTRACT

An analyzer for chemical assays includes a turntable which supports sample containers and reagent containers within a cooled volume and test cells about the periphery of the cooled volume. A probe is carried by a rotating arm for withdrawing liquid from the containers and dispensing the liquid. Fixed stations are also provided in the path of the probe. One such station serves to both wash the tip of the probe and to receive samples for flow-through analysis. Heaters associated with the probe and with the test cells increase the rate of reaction. Curved walls of test cell segments match the optics of an optical analyzer so that light from the analyzer lamp is generally orthogonal to the curved surfaces. The light voltage of the lamp may be controlled as a function of lamp wavelength required for particular assays. The system provides multiple-point calibration and automatic dilution of samples. Multiple aliquots of reagent may be drawn into the probe and then be dispensed into separate test cells. Individual aliquots of sample may be drawn and dispensed with the reagent.

RELATED APPLICATIONS

This application is a division of application Ser. No. 08/404,168 filedMar. 14, 1995, now U.S. Pat. No. 5,597,733, which is a continuation ofSer. No. 08/093,576 filed Jul. 19, 1993, now abandoned, which was aContinuation-in- Part of Ser. No. 07/807,772 filed Dec. 9, 1991, nowU.S. Pat. No. 5,229,074, which is a File Wrapper Continuation of Ser.No. 07/224,059, filed Jul. 25, 1988, now abandoned. All of the aboveapplications are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

Chemical assays, particularly biochemical assays, must often beperformed on a large number of samples taken from test tubes or othersample containers. Further, it is often necessary to perform differentassays on each of the many samples, each assay requiring mixing of oneor more reagents with a sample and performing an analysis such as anoptical analysis. Performing such multiple assays on multiple samplesmanually is very time consuming and subject to error. More recently,robotic systems have been developed to automatically withdraw sampleliquid from sample containers and reagent from reagent containers and tomix the two in test cells for analysis. The sample containers and testcells may be positioned in circular arrays on turntables. One or moreprobes on arms carry sample liquid to the test cells and reagent fromreagent containers to the test cell.

DISCLOSURE OF THE INVENTION

The present invention relates to improvements to automatic analyzers.

In one form of the invention, a turntable removably supports a pluralityof sample containers and a plurality of larger reagent containers in acircular array. A peripheral array of transparent test cells is alsosupported on the turntable. An optical analyzer is positioned toilluminate selected test cells and detect light from the cells. Atranslatable probe is able to withdraw liquid from selected ones of thesample and reagent containers and dispense the withdrawn liquid into aselected test cell. The probe is selectively positionable over allsample and reagent containers and all test cells with translation of theprobe and rotation of the turntable.

Preferably, a cooler cools the sample and reagent containers supportedon the turntable in order to extend the useful life of each. The testcells are grouped as segments which surround, but are thermally isolatedfrom, the sample and reagent containers. A heater is provided to heatthe liquid drawn into the probe before the liquid is dispensed from theprobe. Further, a heater may be provided to heat test cells. The heatingincreases the rate of reaction and insures that all readings areperformed at an appropriate temperature.

Preferably, the probe is positioned on the end of a rotating arm whichis also mounted for vertical translation. A detector may be provided fordetecting the vertical height of the probe, and a level detector may beprovided for detecting the position of the probe relative to liquidwithin a container. The level of liquid in all of the containers maythus be monitored and the amount of immersion of the probe may becontrolled. Optical encoders may accurately indicate the angularposition of each of the turntable and the rotating arm and the height ofthe arm.

A plurality of fixed stations, which need not be cooled with the samplesand reagents on the turntable, may also be positioned along the path ofthe probe but away from the turntable. Preferably, one of the fixedstations is a probe washer. The probe washer comprises a well into whichthe probe may be positioned and a fluid inlet for introducing washerfluid into the well. The washer further includes a conduit at the baseof the well into which the tip of the probe may be positioned. Theconduit is coupled to a flow-through analyzer so that, after washing ofthe end of the probe, the probe may be positioned to inject liquidtherefrom to the flow-through analyzer.

The turntable may include a first tray adapted to carry elongated samplecontainers and the reagent containers and a second tray positionableover and removable from the first tray and coupled to rotate therewith.The second tray is adapted to carry shorter sample containers.

Preferably, the test cells comprise inner and outer transparent wallswhich are curved along inner and outer surfaces. The curved surfacesminimize reflections and chromatic aberrations and thus permit the useof a lamp and lens system having a lower F number of less than 5. Alower power lamp may thus be used. The test cells may be formed incircular segments of multiple cells. Each circular segment comprisesinner and outer curved walls joined by cell dividing walls. A notch maybe provided in the bottom of each segment so that the segment can bedispensed along a narrow ramp into a drawer for disposal after use.

The level of electrical output to a lamp which illuminates the test cellmay be controlled as a function of wavelength of interest in an opticalanalysis. This level control extends the life of the lamp where highelectrical input must be provided to obtain light of particularwavelengths but those wavelengths are not always required. The analyzermay include a grating which receives light from the test cell anddirects different wavelengths of light to different portions of adetector array.

Mixing of sample liquid and reagent introduced into a test cell may beobtained by short, relative movement between the probe and the turntablewhen the probe is inserted into a test cell. Movement may be obtained byoscillating the probe drive and/or the turntable drive.

Preferably, the controller is responsive to bar code input identifyingsamples and bar code inputs which determine particular assay proceduresfor the samples. Those procedures may include a calibration cycle inwhich optical analyses of standard samples from plural, predeterminedcontainers on the turntable are performed to define a calibration curve.Thereafter, the calibration curve may be used to calibrate tests ofsamples from other sample containers. Preferably, any dilution of thesamples is also performed automatically with the system providing ananalysis output as a function of the amount of dilution. The dilutionmay be performed automatically where analysis output levels are found tobe above a highest calibration level, or the dilution may be performedin response to operator instructions.

The analyzer may include a number of motors, each having plural coils. Asingle set of drivers may be coupled to the coils of all of the motors,and selective drivers, each associated with a motor, select one motor ata time. Each selective driver may be coupled in common with all coils ofits motor. The motors are mounted with shock absorbing couplings.

Output from a detector array may be multiplexed and amplified. Theamplifier output is applied through an analog-to-digital converter to acomputer. Through a digital-to-analog converter, the computer adjuststhe gain of the amplifier to provide an output within the range of theanalog-to-digital converter.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescription of a preferred embodiment of the invention, as illustratedin the accompanying drawings in which like reference characters refer tothe same parts throughout the different views. The drawings are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the invention.

FIG. 1 is a plan view of an analyzer embodying the present invention.

FIG. 2A is a partial sectional view of the system of FIG. 1 taken alongthe lines 2--2, with the arm rotated.

FIG. 2B is a side view of the turntable and arm drive mechanism.

FIG. 3 is a view of the probe arm of FIGS. 1 and 2 partially broken awayand enlarged.

FIG. 4 is a schematic illustration of the probe and associated valve andheater pumps.

FIG. 5 is a plan view of a test cell segment in the system of FIG. 1.

FIG. 6 is an unwrapped side view of the test cell segment of FIG. 4.

FIG. 7 is an illustration of light detector circuitry.

FIG. 8 is a schematic illustration of a ramp and drawer for dispensingused test cell segments.

FIG. 9 is a sectional view of the washer/injector station of FIG. 1.

FIG. 10 is an electrical block diagram of the system.

FIGS. 11A and 11B illustrate two sides of a sheet for bar code input ofassays to be performed.

FIG. 12 is an illustration of a motor drive circuit used in the systemof FIG. 1.

FIG. 13A is a partial cross sectional view of an alternative heaterconfiguration supporting the test cell segments.

FIG. 13B is a partial cross sectional view of yet another arrangementfor supporting and driving the test cell segments.

DESCRIPTION OF A PREFERRED EMBODIMENT

A plan view of an analyzer embodying the present invention isillustrated in FIG. 1. The analyzer includes a turntable 20 whichcarries a circular array of 42 sample containers 22 and 14 largerreagent containers 24 which surround the sample containers. Ten testcell segments 26, each having fourteen test cells formed therein,surround the reagent containers. As illustrated in FIG. 2A, a probe 30extends below a rotating arm 32. As illustrated in FIG. 1, the arm 32may be rotated to position the probe 30 over any one of the sample andreagent containers and test cells by rotation of the arms and rotationof the turntable. The arm 32 is then translatable vertically to positionthe tip of the probe 30 within the selected container or test cell andwithdraw or dispense liquid. The probe follows a curved path 34.

As illustrated in FIG. 2A, the sample and reagent containers areisolated from the test cells by a wall 36. This wall allows the innercontainers to be cooled 53 by air flow from a Peltier cooler, to extendthe useful life of the samples and reagents while permitting the mixedsample and reagent in the test cells to be held at a higher temperatureto increase the rate of reaction. Some reagents and other solutionsshould not be refrigerated. Thus, a curved tray 38 is provided forcontainers of such liquids (FIG. 1). The tray positions the containersalong the path 34 of the probe.

In usual procedures, the probe is washed after a sample or reagent isdrawn into the probe to remove the sample or reagent from the sides ofthe probe. Because this washing procedure is performed often, a washingstation 40 is positioned close to the turntable along the path 34. In atypical procedure, 350 milliliters of reagent might be pulled from areagent container 24 with the probe 30. The probe would then bepositioned over and dipped into the washer station to clean reagent fromthe sides of the probe. Then the reagent might be drawn into the probeeven further to create an air pocket before positioning the probe in asample container to draw sample into the probe. Again, the probe wouldbe washed at the station 40. The probe would then be positioned over atest cell, and the sample and reagent would be dispensed into the testcell. The precise time at which the sample and reagent are dispensedinto the test cell would be noted by a controller, and the reactionwould be allowed for some predetermined time before performance of anoptical analysis. Injecting the liquids into the test cell may providesufficient mixing. If not, mixing may be performed by positioning theprobe in the test cell and causing short oscillations of the probe orthe turntable or both by means of their principal drive motors. Becauseof the curved paths of the probe and test cells, driving both togetherresults in an elliptical stirring movement of the probe.

As illustrated in FIG. 3, tubing 42 from the upper end of the probe 30is wrapped around a heating unit 44. Thus, liquid drawn into the probemay be warmed to proper reaction temperature before being dispensed intothe test cell. As a result, the heater 46 (FIG. 2A) positioned below thetest cells at the optical analyzer need not have a large heatingcapacity.

As illustrated in FIG. 4, liquid is drawn into the probe and about theheater 44 through a tube 45 and valve 47 by one of two reciprocal pumps48 and 50. The pumps are of different cross-sectional areas in order toprecisely draw small amounts of liquid or less precisely draw largeramounts of liquid. The two-way spool valve 46 allows buffer solution tobe drawn from a reservoir 52 into the pumps to prime the pumps. Further,in some cases it might be desirable to dispense buffer solution from thereservoir 52 into a test cell. For example, the system may automaticallydispense a measured amount of buffer solution into a test cell with asample to dilute the sample. By diluting samples automatically ratherthan before placement of a sample into the system, errors in computingthe results of an analysis as a function of dilution may be minimized.Also, where the system detects an output from an analysis which is abovea calibration level of the system, the system may automatically dilutethe sample and provide accurate measurements from the diluted sample.Additional pumps and sources of solution may also be provided.

Further details of the turntable and drive mechanism are illustrated inFIGS. 2A and 2B.

The turntable is removably positioned over a drive shaft 60 whichextends through the base of a turntable well 62. The turntable includesa center hub 64 which drops down over the shaft 60 and is keyed theretoby pin 66 carried by the shaft 60. Disks 68 and 70 are mounted to thehub 64 and have holes therein dimensioned to receive conventional testtube sample containers. Test tubes 22 are supported by a lower carrierdisk 72 which is carried by the discs 68 and 70 through struts 73. Anupwardly directed flange 74 supports the reagent containers 24 which arepositioned in larger peripheral holes about the disks 68 and 70. Asillustrated, the reagent containers may be tilted to facilitatewithdrawal of reagent when the reagent level is low.

Test tubes 22 are shown positioned in the turntable to the left of theshaft 60 (FIG. 2); to the right of the shaft, a partially shown optionaltray for smaller sample containers 76 is positioned on the hub 64. Thetray for smaller containers includes a disk 78 having holes therein forthe containers. The disk is carried by a center hub 80 which may bedropped onto the upper end of the hub 64.

The test cell segments 26 are carried by an outer ring 82 which iscoupled to the disk 68 by struts 84. The test cell segments are retainedwithin curved slots in the ring 82 by bullet detents 86.

The entire turntable well may be covered by a cover plate 88 illustratedin FIG. 2. That cover plate has an opening shown by broken lines 28 inFIG. 1 which may be closed by hinged closure 90. With the cover plate onand closed, the sample and reagent containers can be kept cool. Theclosure 90 may be opened for selective replacement of test cell segmentsand sample and reagent containers, and the full plate 88 may be removedto replace an entire turntable or small sample container tray.

An optical encoder disk 94 fixed to the shaft 60 and a set of LEDs anddetectors 96 may be used to provide precise indications of the positionof the turntable to the main controller.

The arm 32 may be rotated by a belt 98 which rotates a lower hub 100about bearings 102. The hub 100 carries a vertical guide post 102 whichrides in a hole in a plate 104. The plate 104 is fixed to the armsupport shaft 106 and thus rotates the arm 32 with rotation of the plate100 and post 102.

The height of the arm 32 is adjusted by means of a screw 108 whichextends through the bearing 102 and plate 100 into the shaft 106. Withrotation of the screw 108 by a belt 110, the shaft and the rotor plate104 may be translated up or down. The plate 104 is detected at itshighest point by a detector 112. The angular position of the arm 32throughout rotation may be detected by a set of LEDs and detectors 114which view an optical encoder 116.

The drive system of an analyzer needs to be simple to assembly, easy tomanufacture, easy to repair, and provide little addition to the noise ofthe analyzer, since it is used in environments which may find excessinstrument noise objectionable. The avoidance of complicated machinedparts and castings is also desirable.

FIG. 2B illustrates the drive to the turntable and probe arm. Threestepper motors M_(T), M_(R), and M_(V) drive the turn table, rotate thearm, and vertically drive the arm. Each is coupled to the system throughshock absorbers. For example, the motor M_(T) is coupled to a mounting202 through a set of four shock absorbing isolators 204. Also, the motordrives a shaft 206 through a rubber coupling 208. The shaft 206 drives abelt 210 which drives a wheel 212 mounted on a shaft 214 carried by abearing 216. The shaft 214 also carries a wheel 218 which drives asecond belt 220. The belt 220 drives a wheel 222 to drive the shaft 60of the turntable. The several wheels and belts provide for a desiredgear ratio in the drive.

Similarly, the motor M_(R) drives the lower hub 100 of the rotating armthrough belts 224 and 98 and the wheels 226 and 228 carried by thebearing 230. The screw 108 is driven directly by the motor M_(V) throughbelt 110.

FIGS. 5 and 6 illustrate a test cell segment 26. The segment comprisesouter and inner walls 118 and 120 joined by dividing walls 122 whichdefine individual test cells. The walls 118 and 120 are frosted at 123along the inner dividers to a height corresponding to the analyzer lightpath in order to intercept light which might pass through the dividerwalls and interfere with measurements. The bottom of the segment is alsotransparent to allow for fluorescence analysis. By forming the cellswith shared dividing walls 122, the number of cells which can beobtained about a given circumference can be maximized, the amount ofplastic used is reduced and the mold is simplified.

As described above, the turntable can be rotated to move a selected testcell into an optical analyzer station illustrated schematically in FIG.2A. At the analyzer, light from a lamp 124 is directed through anaperture 126 and lens system 128 toward the test cell. The light passesthrough holes in the walls 130 and 132 in the well 62 and through thetransparent front and rear walls 118 and 120 of the test cell. The lightis reflected by a mirror 134 to a concave holographic grating 136. Thegrating separates the light according to wavelength and distributes theseparated light along a detector array 138. Thus, the absorption oflight from the lamp 124 by the liquid in the test cell may be determinedas a function of wavelength. Trichromatic or polychromatic correctionsare readily implemented with the data obtained from the array ofdetectors.

The detector circuitry is illustrated in FIG. 7. Signals from theindividual diodes of the array 138 may be selectively amplified bypreamplifiers such as 139 and 141. Where the signal is known to besufficiently large, preamplification is not required. All of the signalsfrom the diodes are multiplexed by a multiplexer 143 to the input of alog amplifier 145. The output of the amplifier 145 is converted to adigital signal by means of an analog-to-digital converter 147 andapplied to a local process controller 164. The controller 164 returns asignal through a digital-to-analog converter 149 to adjust the gain ofthe log amplifier 145. Using an inexpensive 4-bit digital-to-analog 149,the output of the log amplifier can be held within the range of aninexpensive analog-to-digital converter 147.

As illustrated in FIG. 5, both inner and outer surfaces of the front andback walls 118 and 120 are curved. This curve minimizes reflections andaberrations and thus enables the use of an illuminating system having alow F number of less than 5. Prior systems have used test cells withflat walls and have required illumination systems of a high F number toavoid aberrations. The high F number in turn required the use ofhigh-power lamps.

As illustrated in FIG. 6, the test cell segment has a central notch 151formed in its base. This notch facilitates dispensing of used segmentsfrom the analyzer. As illustrated in FIG. 8, a ramp 153, which issufficiently narrow to be received within the notch 15, is providedbelow the opening 28 (FIG. 1) in the turntable cover. After a test cellhas been used, it may be dispensed by pressing a new test cell segmentagainst the used segment to press it down onto the ramp 153. The ramp153 guides the segment into a drawer 155 previously positioned in theanalyzer housing. The drawer has an opening in the rear to receive theramp 153 and is disposable with the used test cell segments.

FIG. 9 illustrates the novel washer station 40. Washer stationstypically include a center well surrounded by a basin 142. Wash liquidis directed upwardly from an inlet 144 in the base of the well, past theprobe 30 to clean the outer walls of the probe and over the wall 146 ofthe well into the basin 142. From the basin, the waste wash liquid isdrained through a conduit 148.

In the present system, the wash solution is introduced through a sideport 150. Below the port 150, an o-ring 152 is provided for receivingand sealing about the end of the probe. The o-ring 152 is at the mouthof an injection station conduit which leads through a pump 156 to aflow-through analyzer 158. It is usual to first wash a probe prior tomoving the probe to an injection station. The combinationwasher/injector of FIG. 6 provides both functions at a single station.The probe is washed as it is lowered into the injection station. Theflow-through analyzer may be of any known type and many differentanalyzers may be provided. Known flow-through analyzers include thoseused for pH and, Other ion detection, CO₂ and O₂. Further, the analyzermight be an optical analyzer.

An electrical block diagram of the system is illustrated in FIG. 10. Thesystem includes a host computer and terminal 160 which receives userinputs, provides user prompts, indicates assays to be performed, andprovides printed reports. The host computer is coupled to a bar codereader 162. Both the sample containers and reagent containers may havebar code labels thereon for identifying the patient and reagent,respectively. The bar code input into the system minimizes clericalerrors.

FIGS. 11A and 11B illustrate two sides of a single sheet which may beused to indicate to the system particular assays which are to beperformed with respect to particular patient samples. It can be seenthat lists of general chemistries, drugs and special chemistries whichcan be detected by the analyzer are listed in human-readable form. A barcode identifying each such assay is associated with each. Each of theprofiles identifies with a single input a plurality of assays to beperformed. After the operator has scanned the patient identifier labelon the sample container to identify the sample to the system, he maydetermine from the patient's chart the particular analyses to beperformed and then indicate the analyses to the system by scanning barcodes of the sheet of FIGS. 11A and 11B.

In addition to identifying assays, the optically encoded sheet mayindicate which of several trays is positioned in the analyzer. Thereagent trays may be loaded beforehand with particular reagents whichare identified to the computer system. The bar code input may be used toindicate to the system which reagent tray is on the turntable. Finally,specific commands may be provided to the system using the bar codeinput.

The bar code input results in less error and is more efficient thaninputting directly into the processor either by keyboard or cursor.

The printer 165 of the system is of a quality which permits the host togenerate a sheet of adhesive labels, each of which identifies the sourceof samples in both human readable form and machine-readable bar code.

In the applications where the instrument is used as a clinical chemistryanalyzer, one or more labels for patient identification can go to theclipboard at the patient's bed or other convenient location, so that thelabel can be attached to any work orders for the patient and anyspecimen drawn from the patient, to be later read by the analyzer.Provision is made through keyboard for optional patient demographics,such as name, doctor, identification numbers and test results.

Further provision is made through keyboard entry or through RS232communications port for demographics as well as test results from otherinstruments, so that they can be logged onto the same report form.

Thus, providing hardware and software system that handles patientdemographics, archiving of prior patient results, generation of bar codelabels coded to patient identification, reading of those labels as partof the setup of the test requirements for each sample, reading of thesheets indicating which tests are to be run and what operations to beperformed, automatically providing location for insertion of appropriatereagents and test samples, running the chemical assays in aself-calibrating system, and reporting the results either by RS232output or by printing a hard copy or by displaying on a graphicsterminal alphanumerically or graphically, or any combination of these asrequired by the operator, increases throughput, minimizes errors andextra hardware.

A local controller 164 is provided to respond to the instructions fromthe host computer 160 and control operation of the many elements of thesystem while collecting data from various sensors. Specifically, thecontroller drives the turntable stepper motor M_(T), the arm rotatingstepper motor M_(R) and the and the arm vertical drive stepper motorM_(V) related encoders E_(T), E_(R) and E_(V). As illustrated in FIG. 2,drivers to the motor coils may be shared in a multiplexed fashion. Eachof several stepper motors which, for example, drive the turntable andarm and various pumps includes four coils 166. The coils are coupled tofour drivers 168 each of which is coupled to a coil of each motor. Aspecific motor to be driven at any instant is selected by a number ofmotor drivers 170, each of which draws current through a common node ofall coils in a motor. Thus, for example, five motors can be driven withonly nine drivers in a multiplexed fashion; whereas 20 drivers would berequired if an individual set of four drivers were provided for eachcoil.

The controller 164 also monitors a level detector LD which is preferablya simple capacitor detector with the metal probe 30 serving as one plateof the capacitor. As the probe contacts the liquid in a samplecontainer, reagent container or test cell, the capacitance changesabruptly. That signal indicates the fluid level so that the availablevolume of liquid can be monitored and the probe need not be dipped deepinto the liquid. Also, at the wash station, the signal provides areference for moving the probe down into the seal of the injectionstation and can verify that wash solution is in the wash station.

The controller also controls the Peltier cooler, the turntable heaterand the probe heater C, H_(T) and H_(P) and responds to associatedsensors. It drives the probe pumps P_(P) and associated valve V. Itcontrols the electrical voltage applied to the lamp L of the opticalanalyzer and the shutter S. It further receives data from the detectorarray D. Also, it controls the pump PA associated with the flow-throughanalyzer and controls and receives data from the analyzer A.

Among the capabilities programmed into the host 160 is the ability tocontrol the voltage level applied to the analyzer lamp 1 in order toextend the life of the lamp. To obtain low frequency light of about 340nanometers, a halogen-filled quartz lamp is used. The lamp must be runvery hot to obtain the 340 nanometer light, and that heat leads to ashorter life. The life of the lamp can be substantially increased byreducing the voltage input where the low wavelength signals are notrequired for a particular sequence of assays.

The host 160 also supports automatic multiple point calibration of thesystem. With standard samples positioned at predetermined locations inthe tray, a series of calibration tests may be run by the system, andthe host uses the results of those tests to plot a calibration curve.The system can then automatically provide calibrated outputs from thetests. Further, if a test provides an output which is above the highestcalibrated level of the system, the system may automatically dilute thesample, or reduce the optical input in time or intensity, to bring theoutput within the calibration range and take into account the dilutionor reduction in input when reporting the results of an analysis. Also,the system may respond to specific user instructions to dilute thesample. This is particularly advantageous where the user knows thesample is too concentrated, but eliminates the potential for user errorin diluting the sample. It is also useful where only a limited amount ofthe sample is available. Dilution allows for a greater number of assayseven though those assays may be performed at the lower end of thecalibration curve.

An alternative embodiment of the analyzer provides a turntable andrelated components of FIG. 1 and FIG. 2A with a modified heater 46providing a channel in heater 231, as shown in FIG. 13A. By thisalternative embodiment, it becomes unnecessary for turntable 20, FIG. 1to support segments 26, as the latter may be caused to slide in thechannel by rotation of the turntable.

Yet another alternative embodiment of the analyzer may also provide forindependent movement of the segments relative to the remainder of theturntable, so that segment position is independent of sample and reagentposition. One possible embodiment of this alternative is indicated inFIG. 13B, wherein heater 232 is provided with groove 233 in the innerwall of the channel holding in position toothed belt 234, which isdriven by a motor or the like, so that certain of the teeth engageappropriately with the segments to move them under the control ofcontroller 164 of FIG. 12. This independence of segment position fromthat of the sample and reagent containers increases the throughput ofthe analyzer, as the sample and reagent containers and the segments caneach be placed optimally for sample and reagent pickup and dispensing bythe probe.

An alternative embodiment of segment 26 of FIG. 6 is to provide 16 ormore individual test cells in each segment to increase the walkawaycapacity of the analyzer.

The software directing the operation of the controller can provideincreased analyzer throughput by causing pump 50, FIG. 4 to aspiratelarger volumes of a reagent than is required for a single assay whenmore than one of the same assay is to be performed.

This procedure, for example, may cause pump 50 to pick up sufficientreagent from one reagent bottle 24, FIG. 1 for ten or more assays andthen to pick up sample for one assay. Pumps 48 and/or 50 dispense thesample and an adequate amount of reagent into the first reaction cup. Asecond sample is subsequently picked up and dispensed with anotheradequate amount of reagent into the second reaction cup withoutreturning to the reagent bottle, and this process is continued untilsome ten samples and aliquots of the reagent have been dispensed. Thus,throughput is greatly increased by the elimination of movement to andfrom the reagent bottle 9 out of the 10 times.

In another example of the bulk handling of reagent, a sufficient amountof reagent is drawn into the probe from one reagent bottle for a numberof assays. The individual aliquots of reagent are then delivered to thetest cells independent of delivery of the samples. Either before orafter delivery of the reagent, aliquots of sample are individually drawnand dispensed. This approach allows for dispensing of pumping fluid withthe sample into the test cell as a diluent. Typical pumping fluidsinclude water, saline and water with surfactant. The approach alsoallows for photoanalysis of blank aliquots of reagent before the samplesare dispensed.

The two bulk methods of delivering reagent may also be used incombination. For example, one reagent may be drawn in bulk and deliveredto multiple test cells for blank readings, and a second reagent may thenbe drawn into the probe in bulk and then dispensed to individual testcells with individual aliquots of sample.

The design of washer/injector station, FIG. 9, provides a volume ofbasin 142 which does not drain quickly into outlet 148. This volume,which is filled with wash liquid from overflow of center well 140,provides a place for the temporary immersion of probe 30 to wash bothoutside and inside of the probe while pumps 48 and/or 50 are moved toexpel sample, or reagent, or pumping solution, or all three. Thisimmersion of the probe during initial was eliminates the atomization ofpotentially infectious or hazardous solutions which could occur duringdispensing of solutions into the air over the washer station.

A further benefit of this feature is that this volume of fluid in thebasin provides a prewash of the probe. When the probe is introduced intothe center well, the probe causes less contamination of the washsolution in the center well. The probe is cleaner as the result of thedouble wash, and the flow rate of the wash solution may be reduced,conserving this solution and reducing operating cost of the analyzer.

Since a lamp has a predictable stabilization time period, it isfrequently possible to predict when the lamp's voltage can be reduced orturned off completely when it is not needed for a reading. Included inthe preferred embodiment of the analyzer is time-dependent control oflamp 124 of FIG. 2A. By reducing the voltage applied to the lamp whenintervals between measurements occur--such as waiting for slow endpointchemistries, or delays while tests are being set up--the life of thelamp can be extended greatly, reducing service time and expenses.

Additional life extensions may be achieved, when longer delays occur, byutilizing the lamp control circuit to completely turn off its voltageautomatically until its warm-up time requires turn-on of the lamp, sothat its light output will be stable when measurements of samples are tobe made. Thus, the whole instrument can be left on to maintaintemperature control of critical areas without the lamps being on and itslife shortened.

While this invention has been particularly shown and described withreferences to preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the spirit and scope of theinvention as defined by the appended claims. For example, the systemdescribed allows for only absorption-type tests using the test cells.Fluorescent-type tests using optical filter wheels and with the detectorat right angles to the incoming light are also readily implemented.

What is claimed is:
 1. An analyzer system comprising:a plurality ofcontainers for separately storing samples and reagent and test cells inwhich samples and reagent are to be dispensed; a probe for drawingsample and reagent from respective containers and dispensing the sampleand reagent in the test cells; and electronic control which causes theprobe to draw an amount of reagent sufficient for plural tests and tosubsequently draw sample and dispense sample and reagent for pluraltests by sequentially, for each test, drawing sample for an individualtest and dispensing sample and reagent for the individual test withoutdrawing additional reagent between tests.
 2. An analyzer system formixing samples and reagents and performing an optical analysis thereof,the analyzer comprising:a plurality of sample containers containingsample liquid in a first rotatable circular array, each of the pluralityof sample containers being removable from the analyzer independentlyfrom each other, and a plurality of larger reagent containers forcontaining reagent liquid in a second rotatable array concentric withthe first rotatable circular array, each of the plurality of largerreagent containers being removable from the analyzer independently fromeach other and independently from the sample containers; a thirdrotatable circular array of removable transparent test cells surroundingthe plurality of reagent containers and sample containers, the testcells being removable from the analyzer independently from the pluralityof sample containers and reagent containers; an optical analyzerpositioned adjacent to the third rotatable array which illuminates aselected test cell and detects light from the cell to provide a signalrepresentative of a property of liquid in the test cell; a translatableprobe which withdraws liquid from selected ones of the sample containersand the reagent containers and dispenses withdrawn liquid into aselected test cell to mix liquid from the sample and reagent containers,the probe being selectively positionable over all sample and reagentcontainers and all test cells by translation of the probe and rotationof the first, second and third rotatable arrays; and a programmablecontroller and drive assembly, the controller being programmed forrotating the first, second and third rotatable arrays, translating theprobe and causing the probe to withdraw and dispense sample liquid andreagent liquid to mix reagent and samples in test cells and performtests as programmed for individual samples, the controller beingprogrammed to dispense liquid from a common reagent container intoplural test cells and liquid from a common sample container into pluraltest cells, the controller being programmed to cause the probe to drawan amount of reagent sufficient for plural tests and to subsequentlydraw sample and dispense sample and reagent for plural tests bysequentially, for each test, drawing sample for an individual test anddispensing sample and reagent for the individual test without drawingadditional reagent between tests.
 3. An analyzer system as claimed inclaim 2 further comprising a plurality of fixed stations adjacent to theturntable and positioned along a path of the probe away from theturntable.
 4. An analyzer system as claimed in claim 2 wherein the probeis positioned on the end of a rotating arm.